(See also Overview of Sprains and Other Soft-Tissue Injuries Overview of Sprains and Other Soft-Tissue Injuries Sprains are tears in ligaments (tissues that connect one bone to another). Other soft-tissue injuries include tears in muscles (strains) and tears (ruptures) in tendons (tissues that connect... read more and Finger Fractures Finger Fractures Common finger fractures include avulsion fractures and crush fractures of the fingertips. When a fingertip is crushed, it is tender and swollen, and the nail may be bluish black and raised up... read more .)
Mallet finger usually results when the tendon that attaches bone to muscle in the fingertip is torn. This tendon (called the extensor tendon) is used to straighten the fingertip. Usually, the tendon is torn when a force causes the fingertip to bend more than it normally does. A common cause is a baseball that hits the fingertip and jams it. Thus, mallet finger is sometimes called baseball finger.
One or more fingers may be affected. Sometimes the joint is also dislocated.
When the tendon tears, it may pull a piece of bone from the finger (called an avulsion fracture). When an avulsion fracture occurs, the cartilage at the end of the affected bone (the joint surface) is also fractured.
The finger is usually painful, swollen, and bruised immediately after the injury. The joint remains bent. The person cannot straighten it. Occasionally, blood collects under the nail (called a subungual hematoma Subungual hematoma Even a minor injury to the finger may cause changes in the nail. The nail may develop a small spot of white discoloration that starts at the injured location and grows out with the nail. Severe... read more ).
Usually, doctors straighten the finger, then place a splint on it to hold it in a position that is bent slightly upward (in extension). The splint is worn for 6 to 8 weeks.
Rarely, when a fracture involves a large part of the joint surface or when the joint is dislocated, surgery is needed.